1. Field of the Invention
This invention relates to a vacuum cleaner.
2. Related Background Art
Historically, vacuum cleaners have comprised a permeable filter bag for separating entrained dirt and dust from the suction airflow and for collecting the separated dirt and dust. However, many vacuum cleaners nowadays comprise a cyclonic separator, which separates entrained dirt and dust from the suction airflow and deposits it in a receptacle for emptying.
A disadvantage of cyclonic separators compared with filter bags is that cyclonic separators do not always offer the level of filtration efficiency that is achieved with filter bags. In order to overcome this problem, it is commonplace to mount a filter downstream of the cyclone separator. In this manner, virtually all dust and dirt is removed from the suction airflow before the air enters the fan of the vacuum cleaner, with the majority of dirt and dust, including all coarse and fibrous material, being retained in the cyclone separator, and the remaining fine dust being retained on the filter.
Over time, the build up of fine dust on the filter reduces the airflow through the vacuum cleaner and hence the performance of the cleaner is affected unless the filter is periodically replaced or cleaned.
European Patent Application No. 1 195 125 discloses an upright vacuum cleaner having a cyclonic separator and a filter mounted downstream of the cyclonic separator. The filter is located in a chamber directly above the cyclone chamber and is only accessible once the detachable cylindrical dirt-collection bin is removed from the cleaner. In order to remove the filter, the user must reach inside the cleaner to release the perforated cyclone air outlet screen, which is retained by a conventional bayonet fixing, and withdraw the filter from its chamber. The filter may then be washed, dried, and returned to the cleaner.
A disadvantage of the above-mentioned arrangement is that the filter is mounted out of sight and thus there is a tendency for the user to forget to clean the filter regularly. Also, because the filter is mounted out of sight, there is a risk that the cleaner could be used without the filter: it will be appreciated that this will affect the performance and reliability of the cleaner. Another disadvantage of the above-mentioned arrangement is that the filter is awkward to remove and the removal involves handling the filter, which is often coated in dirt and dust.
International Patent Application WO02/28260 discloses an upright vacuum cleaner having a cyclonic separator and a filter mounted downstream of the cyclonic separator. The cyclonic separator and the filter are mounted together in a cylindrical separator unit, which is removable from the vacuum cleaner body for emptying and maintenance. The filter is mounted in the top portion of the separator unit and a transparent cover is provided at the top of the unit, which can be removed once the unit has been disengaged from the cleaner to allow access to the filter inside the unit. The filter then has to be removed from the unit by hand. Following filter cleaning, the filter is replaced in the unit, the cover closed, and the entire separator unit replaced on the vacuum cleaner body.
The complexity of the filter cleaning operation, and the associated exposure of the user to dirt and dust, are likely to be a disincentive to filter maintenance, which may very well compromise sustained efficient operation of the vacuum cleaner.
We have now devised a vacuum cleaner which alleviates the above-mentioned problems.